Problems running VM and connecting to internet

Dear Sir,

I am a new Open Nebula user, I am having some problems running Windows Server 2008 VMs :

  • After about an hour running the VM, it goes to the unknown state everytime I instantiate it.

  • I try to set a network of 5 VMs, but from the 5 , one of the VMs cannot connect to the internet.

What could be the cause of these problems ?